Modern Magic: A Practical Treatise on the Art of Conjuring

At this point a contretemps may arise, for which it is well to be prepared. The person interrogated may possibly forget the relative position of the two colours, and may, therefore, ask to see again how the cards are placed; or some person may have seen or suspected that you have already displaced them, and may make a similar request for the purpose of embarrassing you. In order to be prepared for such a contingency, it is desirable, after you make the pass as above mentioned, not to allow the two halves of the pack to immediately coalesce, but to keep them still separated by the little finger. If you have done this, and for any reason it becomes necessary to show the cards a second time in their original condition, you have only to again make the pass, in order to bring them back to the same position which they occupied at first, making it a third time in order to effect the change.